Ultra-depleted 2.05 Ga komatiites of Finnish Lapland: Products of grainy late accretion or core-mantle interaction?
- Autor(en)
- Igor S. Puchtel, Andrea Mundl-Petermeier, Mary Horan, Eero J. Hanski, Janne Blichert-Toft, Richard Walker
- Abstrakt
Rhenium-Os, Ptsingle bondOs, Smsingle bondNd, Lusingle bondHf, and Hfsingle bondW isotope data, together with lithophile trace element and highly siderophile element (HSE: Re, Os, Ir, Ru, Pt, and Pd) abundances, are reported for 2.05 Ga Jeesiörova and Kevitsa komatiites from the Central Lapland Greenstone Belt, Fennoscandia, Finland. Both komatiites are closely genetically related, with the Kevitsa dikes having served as feeding magma conduits to the Jeesiörova pillowed and massive lavas. The parental komatiite magma is estimated to have contained ~25 wt% MgO and was, thus, derived from a mantle source at least as hot as those of some of its late Archean counterparts. A suite of Jeesiörova and Kevitsa whole-rock komatiite samples and olivine and chromite separates define an internal Resingle bondOs isochron with an age of 2049 ± 13 Ma and an initial γ187Os = −0.2 ± 0.2 (2SE), indicating long-term chondritic Re/Os in the mantle source. By contrast, Ptsingle bondOs data for a set of Jeesiörova chromite separates define an average initial μ186Os = +29 ± 2 (2SE), indicating a long-term history of suprachondritic Pt/Os in the mantle source. The absolute HSE abundances in the mantle source of the Jeesiörova-Kevitsa komatiite system are estimated to have been 120 ± 5% of the present-day Bulk Silicate Earth (BSE). This is the first komatiite system for which excess HSE in the mantle source, relative to modern BSE, has been documented.
- Organisation(en)
- Department für Lithosphärenforschung
- Externe Organisation(en)
- University of Maryland, College Park, University of Oulu, Carnegie Institution for Science, Université de Lyon
- Journal
- Chemical Geology
- Band
- 554
- Anzahl der Seiten
- 23
- ISSN
- 0009-2541
- DOI
- https://doi.org/10.1016/j.chemgeo.2020.119801
- Publikationsdatum
- 11-2020
- Peer-reviewed
- Ja
- ÖFOS 2012
- 105105 Geochemie
- Schlagwörter
- ASJC Scopus Sachgebiete
- Geochemistry and Petrology, Geology
- Link zum Portal
- https://ucrisportal.univie.ac.at/de/publications/5a3582ff-1202-4604-a446-5bdd9205d1d0